Fluid pressure circuits



Nov. 24, 1959 D. J. CAMERON FLUID PRESSURE CIRCUITS Filed Jan. 18, 1956 This invention'relates to fluid pressure circuits and more particularly to a fluid pressure supply circuit for fluid pressure operated motors which includes a means for conservation of the pressure fluid required to operate the motors.

The fluid pressure circuit of this invention, in its preferred embodiment, is particularly adapted for use with presses wherein the pressure applying member or press head is operated by'piston type fluid pressure operated motors and the full force of the press head is required only at the end of the operative stroke of the head. One or more actuating motors are used to move the press head through its stroke'of operation and holding motors are used to apply additional force to the press head only" at the end of its operative stroke where it engages the workpiece.

Since the holdingmotors are actuated only at the'end of the operative stroke of the presshead, it has been common to exhaust one side of the pistons of these motors during the operative stroke of the press head and the other side of the pistons of these motors during the inoperative stroke of the press head. This manner of operating the holding motors exhausts rather large volumes of pressure fluid during one stroke of thepress and requires a rather large volume of readily available pressure fluid to. operate the press; I such presses are connected to a source of pressure fluid, the volumesof pressure fluid required by. the presses placesan overload on the source of pressure fluid and at times results in a lack of fluid of suflicient pressure to operate all of the presses. j

The fluid pressure circuit of thisinvention provides a means for conservation of the pressure fluid required to operate the holding motors by recirculating the pressure fluid in the motors'during the entire. inoperativestroke of the press head and during most of the operative stroke of the press head: The pistons of theholding cylinders are only exhausted to.one side immediately prior to the end of the operative stroke of the press head and before actuation of the holding'motors to apply full force to the press head at the end of the operative stroke. ,By so recirculating the pressure fluid during the entire inoperative stroke of the press head and during most of the operative stroke of the head, the large volumes of pressure fluid exhausted in priortpresses are thereby'saved to appreciably reduce the volume of pressure fluid required to operate the press and to also insure that there is always a readily available supply of fluid of suflicient pressure for the press. 6

The primary object of this invention is to provide a newa nd improved fluid pressure supply circuit which includes a manner of conservation of the pressure fluid required to operate a fluid pressure operated motor.

This and other objects of this invention will be readily apparent from the following specification and drawing wherein the drawing illustrates schematically a fluid pressure supply circuit according to this invention.

When a number of l conduit 22 with one side t 2,913,879 Patented Nov. 24, 1959 Referring now to the drawing, a pressure applying member or press head 2 is movable toward and away from a press bed 4 which supports the usual workpiece (not shown). A'nu'mber of compressed air operated motors are connected to the press head 2, with motor 6 being an actuating motor and motors 8, 10, 12, and 14 being holding motors, as will be described. Each of the motors includes a cylinder 16, a piston 18 slidably' mounted in'the cylinder and a piston rod20 secured to piston 18 and to the press head 2.

A source of compressed air (not shown) is connected to a conduit 22 which includes a filter 23 to remove impurities from the air. A branch conduit 24 connects conduit 22 with one side of a pressure regulating valve 26 and a conduit 28 connects the other side of the valve with a conduit 30 which is connected to a surge tank 32.

operated piston operatively connected to valve 52.

g V to conduit 30, and 'a' conduit 54 connects the other side of valve 52 with cyl 6 to the upper side of f One side of valve 52 is connected inder 16 of the actuating motor piston 18 of this motor. A. branch conduit 56 connects 58 and a conduit 60 connects the other side of valve 58 sure operated pistons 64 which are operatively connected to valves 66. for each of the holding motors 8, 10, 12 68 connects conduit 22 with one.

and 14; conduit side of a solenoid operated valve 70 and the other side of the valve is connected to the air pressure operated piston 72 0f valve 40 by means of a conduit 74.

A branchjconduit76 connects conduit 30 with valve 66, and'a conduit 78 '16 of holding motor 8 of the motor. of valve 66 to of the piston l8 of this motor. A conduit 82 leads from conduit 30 to cylinder 16'of vmotor 10 to the upper side ofpiston 18 of this motor. A branch-conduit 84 leads from conduit 82 to one side of valve 66 and a conduit 86 leads from the other side of the valve to. cylinder 16 of motor 10 to the lowerside of the piston'18 of the leads from conduit 76 to cylinder, to the upper side ofthe piston 18 A conduit -leads from the other side motor, A conduit 88 leads from conduit 30 to one side i of valve .66 and a conduit 90 leads from the other side of the valve to cylinder 16 of motor 12 to the lower side of piston 18 of this motor. A conduit 92 leads from conduit 88 to cylinder 16 of motor 12 to the upper side of the piston- 18 of this motor. A conduit from conduit 30 to cylinder 16 of motor side of the piston 18 of this motor, and a from one side of valve 66 to the cylinder 16 of motor 14 to the lower side ofpiston 18 of this motor. The other side of valve 66 is connected to conduit 30.

Valves 40, 52, and 66 are of similar construction and are spring biased to one position and movable to another position by means of air pressure admitted to one side of pistons 72', 50, and 64, respectively. Piston 72 is'con trolled by solenoid operated valve 70; piston 50 is con 14 to the upper trolled by solenoid operated valve 46; and pistons 64 3 are controlled by solenoid operated valve 58. The valves and air pressure=operated pistons are of known make and thev details thereof are not shown inthe drawings since 1 they form no part of this invention.

of a solenoid operated valve cylinder 16 of motor 8 to the lower side 94 leads conduit 96 leads In the raised position of the press head 2, as shown in v the drawing, the soleniod of valve 46 is deenergized so that valve 46 disconnects conduits 44 and 48 and connects conduit 48 with exhaust through outlet 98 of valve 46. This allows valve 52 to be spring biased to a position to disconnect conduit 54 from conduit 30 and open the upper side of cylinder 16 of motor 6 to exhaust through conduit 54 and valve 52. The soleniod of valve 70 is also deenergized so that valve 70 connects conduit 74 with exhaust through outlet 100 of the. valve. This. allows valve 40 to be spring biased to a position to connect conduit 22 with conduit 42 so as to supply air under line pressure to the lower side of cylinder 16. of motor 6. The line pressure holds piston 18 in the upper portion of the cylinder, as shown in the drawing, to hold the press bed in its raised position.

The soleniod of valve 58 is also deenergized so that. valve 58 connects conduits 60 and 62 with exhaust;

through outlet 102 of the valve. This allows valve 66 of; motor 8 to be spring biased to a position to connect conduits 76 and 80 so that both sides of piston 18 of,

motor 8 are subject to surge tank pressure. Similarly, valve 66 of motor is spring biased to a position to connect conduits 84 and 86 so that both sides of piston 18 of motor 10 are subject to surge tank pressure; valve 66 of motor 12 is spring biased to a position to connect conduits 88 and 90 so that both sides of piston 18 of motor 12 are subject to surge tank pressure; and valve 66 of, motor 14. is spring biased to a position to connect conduits 30 and 96 so that both sides of piston 18 of motor 14 are subject to surge tank pressure.

Thus. in the raised position of the press head 2, both sides of the pistons 18 of the holding motors 8, 10, 12, and 14 are subject to surge tank pressure, while the lower side of piston 18 of motor 6 is subject to line pressure and the upper side of the piston is open to exhaust so that motor 6 will hold the press head in raised position.

A battery 104. is grounded at 106 and connected to a manually operable switch 108 by means of conductor 110. The switch contact 112 of switch 108 is-connected to an electric timer 114 by means of conductor 116. A conductor 118 connects the timer with the solenoid of valve 46 which is grounded at 120, and a conductor 122 connects conductor 118 with the solenoid of valve 70 which is grounded at 123. A conductor 124' connects conductor 118 with one contact of a normally open limit switch 126 and a conductor 128 connects the other contact of the limit switch with the solenoid of valvev 58v which is grounded at 130.

Assuming now that the operator desires to lower the.

press head 2 so as to move the press head against the workpiece which is supported on the press bed; switch 108 is manually closed so as to connect conductors 110 and 116 with battery 104 and energize the solenoids of' valves 46 and 70 as well as the electric timer 114. When the solenoid of valve 46 is energized, valve 46 is moved toa position to connect conduits 44 and 48 and disconnect conduit 48 from exhaust through outlet 98 of the valve. This will admit air under line pressure to piston 50 so that the piston will move valve 52 to a position wherein conduit 54 is connected with conduit 30 to admit air under surge tank pressure to cylinder 16 of motor 6 to the upperside of piston 18 to force the pistonv sure air, admitted through conduit 54. This will move.

the press; head 2 through its operative stroke or lower th Press head. During. movement of the; press. head 2 from, its raised, positionto. its lowered position. through.

4 its operative stroke, air is recirculated from the lower sides of the pistons 18 of each of the holding motors 8, 10, 12, and 14 to the upper sides of the pistons since each of the valves 66 remain in a position so as to connect conduits 76, 84, 88, and 30 with conduits 80, 86, 90, and 96, respectively.

As the press head 2 moves downwardly on its operative stroke, it will engage contact 132 of limit switch 126 adjacent the end of the stroke so as to close the switch and energize the solenoid of valve 58. Energization of the solenoid moves the valve to a position to connect conduits 60 and 62 with conduit 56 to admit air under line pressure to pistons 64 so that the pistons will move valves 66 to a position to disconnect conduits 80, 86, 90, and 96 from conduits. 76, 82, 88, and. 30, respectively, and open the former conduits to exhaust through valves 66. This will exhaust the limited volume of air remaining in the space between the lower side of the pistons 18 of the holding motors and the lower wall of the cylinders 16 and allow air under surge tank pressure in conduits 78, 84, 92, and 94 to be applied against the upper sides of'pistons 18 of the holding motors so as to cause the holding motors and the actuating motor 6 to apply a.

greatly increased force against the workpiece on the press bed 4.

After the required amount of time allowed by the electric timer 114, the circuit is broken between conductors 116 and 118 so as to deenergize the solenoids of valves 46, 58, and 70. Deenergization of the solenoid of valve. 46 moves the valve to a position so as to disconnect conduit. 48 from, conduit 44 and connect conduit 48 with exhaust through the outlet 98 of the valve. This will exhaust the air under line pressure from piston 50 and allow valve 52 to be spring biased to a position so as to connect conduit 54 with exhaust through the valve. Thus, the air under surge tank pressure between the upper side of the piston 18 of motor 6 and the upper wall ofcylinder 16 will be exhausted so as to allow piston 18 to be moved upwardly within the cylinder.

Deenergization of the solenoid of valve 70 moves the valve to a position to disconnect conduit 74 from conduit 68 and connect conduit 74 to exhaust through the outlet 100. of the valve. This will exhaust the air under line pressurefrom piston 72 and allow valve 40 to be spring biased to a position to connect conduit 22 with conduit 42 so as to admit air. under line pressure to cylinder 16 of the actuatingmotor 6 to the lower side of piston 18. This will move the piston of motor 6 upwardly within cylinder 16 so as to raise the press bed 2 and move the pressbed through its inoperative stroke. As the piston 18 of motor 6 moves upwardly within cylinder 16, the air under surge tank pressure between the upper side of the piston and the upper wall of the cylinder will be exhausted through conduit 54 as previously described.

Deenergization of the solenoid of valve 58 moves the valve to a position to connect conduit 60 to exhaust through the outlet 102 of the valve and disconnect conduit '60 from conduit 56. This will cause spring biased pistons 64 to move valves 66 to the position shown in the drawing so as to disconnect conduits 80, 86, 90, and 96 from exhaustthrough the valves 66 and connect these conduits with conduits 76, 84, 92, and 94, respectively, to admit air under surge tank pressure to the cylinders 16 of the holding motors to the lower sides of the pistons 18 of these motors. Thus, both the upper and lower sides of the pistons 18 of the holding motors will be subject to surge tank. pressure as the press bed 2 is moved to a raised position on its inoperative stroke by means of the actuating motor 6. Thus, the press head 2 and the fluid pressure supply circuit are readied for another cycle of operation.

It will be noted that when the press head 2 is moved downwardly on itsoperative stroke that the air under surge tankpressurebetween the lower sides of the pistons. 18.;and thelower wallof thecylinder' 16 of the holding motors is' recirculated'through valve 66rather than being exhausted to the atmosphere. only' t'helimited volume of air remaining between the lower sides of the; pistons 18 of tbe holding motors and the lower wallsof the cylinders 16 is exhausted immediately prior to the end of the operative stroke before actnationgof the holding motors. No air is exhausted between the uppergsides of the pistons 18 of the holding motors and the upper walls of the cylinder 16 during the inoperative stroke of the press bed as it moves to a raised position. Thus, a considerable saving of air is eflected by the fluid pressure supply circuit of this invention since only the minimum amount of air is exhausted during one stroke of the press.

Although the fluid pressure supply circuit of this invention has been shown and described in conjunction with a press, it will be appreciated that the supply circuit is applicable to any long stroke operation where full force is necessary only at the end of the stroke. The single actuating motor 6 is suflicient to move the press bed through the stroke of operation, and the holding motors 8, 10, 12, and 14 are only necessary immediately prior to the end of the operative stroke of the press. By recirculating the air between the upper and lower sides of the pistons of the holding motors during the entire inoperative stroke of the press and during most of the operative stroke of the press, these motors neither aid nor hinder the movement of the press bed nor do they require any volume of air during this movement.

While a specific embodiment of this invention has been shown and described, various changes and modifications may be made within the scope and spirit of the invention.

I claim:

1. In combination with a pressure applying member movable to at least two positions, first differential fluid pressure operated piston motor means operatively connected to said member for moving said member to either of said positions, second differential fluid pressure operated piston motor means operatively connected to said member, a source of fluid pressure, conduit means from said source to either side of said first and second piston motor means, first valve means in said conduit means to said first piston motor means operative to allow fluid pressure to operate against one side of said piston motor means and open the other side of said first piston motor means to exhaust to cause said first piston motor means to move said member to one of said positions, second valve means in said conduit means to said second piston motor means selectively and alternately operable independently of said first valve means to allow fluid pressure to operate against both sides of said second piston motor means or to allow fluid pressure to operate against one side thereof and open the other side thereof to exhaust, means for actuating said first valve means to control actuation of said first motor means to move said member to said one of said positions, and control means automatically operable during one portion of the movement of said member to said one of said positions for controlling actuation of said second valve means to allow fluid pressure to operate against both sides of said second piston motor means.

2. In combination with a pressure applying member movable to at least two positions, first differential fluid pressure operated piston motor means operatively connected to said member for moving said member to either of said positions, second differential fluid pressure operated piston motor means operatively connected to said member, a source of fluid pressure, conduit means from said source to either side of said first and second piston motor means, first valve means in said conduit means to said first piston motor means operative to allow fluid pressure to operate against one side of said piston motor means and open the other side of said first piston motor means to exhaust to cause said first piston motor means to move said member to one of said positions, second valve means in said conduit means to said second piston motor means selectively'and alternately operable inde pendently of said first valve means to allow fluid pressure" to operate against both sides of said second piston motor means or to allow fluid pressure to operate against one side thereof and open the other side thereof to exhaust, means for actuating said first valve means to control actuation] of said first motor means to move said member to said one of said positions, and mea'ns automatically operable during one portion ofthe movement of said member to said one of said positions for controlling actuation of said second valve means to allow fluid pressure to operate against one side of said second piston motor means and open the other side thereof to exhaust whereby said first and second piston motor means coopcrate to move said member to said one of said positions during said one portion of the movement of saidmember.

3. In combination with a pressure applying member movable between non-pressure applying and pressure applying positions, first differential fluid pressure operated motor means operatively connected to said member for moving said member between said positions, second differential fluid pressure operated motor means operatively connected to said member, first means for applying a diflerential fluid pressure to said first motor means to cause said first motor means to move said member between said positions, second means selectively and alternately operable independently of said first means to apply equal pressure to said second motor means during the entire period of movement of said member from said pressure applying position to said non-pressure applying position and during the major portion of the period of movement of said member from said non-pressure applying position to said pressure applying position or to apply differential fluid pressure to said second motor means during the remaining portion of the period of movement of said member from said non-pressure applying position to said pressure applying position, and control means automatically operable during the remaining portion of the period of movement of said member from said non-pressure applying position to said pressure applying position for actuating said second means to apply differential pressure to said second motor means whereby said first and second motor means cooperate to move said member only during the remaining portion of the period of movement of said member to said pressure applying position.

4. In combination with a pressure applying member movable between non-pressure applying and pressure applying positions, first differential fluid pressure operated motor means operatively connected to said member for moving said member between said positions, second differential fluid pressure operated motor means operatively connected to said member, a source of fluid pressure, conduit means from said source to either side of said first and second motor means, first valve means in said conduit means to said first motor means operative to allow fluid pressure to operate against one side of said motor means and open the other side thereof to exhaust to cause said first motor means to move said member between said positions, second valve means in said conduit means to said second motor means selectively and alternately operable independently of said first valve means to allow fluid pressure to operate against both sides of said second motor means during the entire period of movement of said member from said pressure applying position to said non-pressure applying position and during the major portion of the period of movement of said member from said non-pressure applying position to said pressure applying position or to allow fluid pressure to operate against one side thereof and open the other side thereof to exhaust during the remaining portion of the period of movement of said member from said non-pressure applying position to said pressure applying position, means for actuating said first valve means to control actuation of said first motor means to move said member between said positions, and control. means automatithe period of movement of said member to move said member to said pressure applying position.

- ReferencesCited in the file of this patent 7 i UNITED. STATES PATENTS Astfalc'k Mar. 12, 1912 Ferris LL.. July 5, 1932 Keel May 9, 1939 Audemar May 20, 1952 Cross Apr. 30, 1957 

